javascript _(variable_name) 在javascript中是什么意思？
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What does _(variable_name) mean in javascript?
提问by Charles Gao
I came across the following javascript code:
我遇到了以下 javascript 代码：
this.removeEdge = function(source, target) {
if(!_states[source]) return;
var children = _states[source].children,
index = _(children).indexOf(target);
if(index !== -1) children.splice(index, 1);
};
What does _(children) mean?
_(儿童)是什么意思？
回答by zzzzBov
_is a valid variable identifier in JavaScript, and could theoretically refer to anything. Using _(...)with function syntax implies that _is a function.
_是 JavaScript 中的有效变量标识符，理论上可以指代任何东西。使用_(...)with 函数语法意味着这_是一个函数。
That said, it is commonly used by the underscore.jslibrary, however if you're looking at minified code, it's quite possibly being used as another single-character variable name to save on file size.
也就是说，它通常由underscore.js库使用，但是如果您正在查看缩小的代码，它很可能被用作另一个单字符变量名称以节省文件大小。
In your example provided, it appears that underscore.js is being used to treat childrenas a collection, so that the indexOffunctioncan be applied to the collection. This would be similar to calling:
在您提供的示例中，underscore.js 似乎被用作children集合，以便可以将该indexOf函数应用于集合。这类似于调用：
_.indexOf(children, target);
回答by jahmezz
Came looking for an answer to this and managed to find one. The _(variable) statement wraps underscore around the variable. According to this linkin the "Object-Oriented and Functional Styles" section,
来寻找这个问题的答案并设法找到了一个。_(variable) 语句用下划线包裹变量。根据“面向对象和功能样式”部分中的这个链接，
index = _(children).indexOf(target);
is equivalent to
相当于
index = _.indexOf(children, target);
The first is written in object-oriented style, which allows chaining of functions. Their example is as follows:
第一个是以面向对象的风格编写的，它允许链接函数。他们的例子如下：
_(lyrics).chain()
.map(function(line) { return line.words.split(' '); })
.flatten()
.reduce({}, function(counts, word) {
counts[word] = (counts[word] || 0) + 1;
Each of these functions returns the underscore function wrapping lyrics, allowing chained manipulation of the lyrics variable.
这些函数中的每一个都返回包装歌词的下划线函数，允许对歌词变量进行链式操作。
Underscore changelog:
下划线变更日志：
0.4.0 — November 7, 2009: All Underscore functions can now be called in an object-oriented style, like so: _([1, 2, 3]).map(...);. Original patch provided by Marc-André Cournoyer. Wrapped objects can be chained through multiple method invocations. A functions method was added, providing a sorted list of all the functions in Underscore.
0.4.0 — 2009 年 11 月 7 日：现在可以以面向对象的方式调用所有 Underscore 函数，如下所示：_([1, 2, 3]).map(...);。Marc-André Cournoyer 提供的原始补丁。包装的对象可以通过多个方法调用链接起来。添加了一个函数方法，提供了 Underscore 中所有函数的排序列表。
